[en] High-pressure X-ray diffraction studies have been performed on ThS up to 40 GPa using synchrotron radiation and a diamond anvil cell. The measured value of the bulk modulus B0=145 GPa is in disagreement with a previous measurement. The high-pressure behaviour indicates a phase transformation to ThS II starting at 15 to 20 GPa. The transformation is of second order nature, the resulting structure can be described as distorted fcc. (orig.)